M. hyo is a bacterial pathogen that causes enzootic pneumonia in swine. Enzootic pneumonia is a chronic disease that results in poor feed conversion, stunted growth and predisposition to secondary pulmonary infections. M. hyo is easily transmitted through respiratory tract secretions and by sow-to-piglet transmission, and is highly prevalent on pig farms. Approximately 99% of US swine herds are infected, costing the swine industry about $300 million annually.
The majority of known vaccines against M. hyo have been based on adjuvanted inactivated whole cell preparations of M. hyo. In addition, vaccines based upon immunogenic polypeptides or proteins may be synthesized or prepared by cloning and recombinant expression of M. hyo genes. M. hyo genes capable of expressing such polypeptides or proteins in vivo may also be used as vaccines.
Examples of whole cell inactivated M. hyo vaccines include RESPISURE and STELLAMUNE, commercially available from Pfizer Inc., USA.
In addition, several recombinantly produced immunogenic polypeptides and proteins of M. hyo that may be useful as subunit vaccines have been described. International Patent Publication WO 96/28472 describes six protein antigen species of M. hyo at molecular weights of 46-48, 52-54, 60-64, 72-75, 90-94 and 110-114 kilodaltons, and discloses partial protein sequences of the 52-54, 60-64 and 72-75 kilodalton antigens and the full length nucleotide and amino acid sequences of the 46-48 kilodalton antigen.
The cloning of the gene encoding the M. hyo protein P46, i.e. p46, was also described by Futo et al. (1995; J. Bacteriol 177:1915-1917). The same group showed that the in vitro expressed gene product was useful in diagnosing antibody responses to M. hyo infections without cross reactivity to other Mycoplasma species (Futo et al., 1995, J. Clin. Microbiol. 33:680-683). The sequences and diagnostic uses of the p46 gene described by Futo et al. are further disclosed in European Patent Publication No. 0 475 185 A1.
Wise and Kim (1987, J. Bacteriol., 169:5546-5555) report that there are four integral membrane protein species in M. hyo, named p70, p65 (P65, supra), p50 and p44, and that the latter three are modified by covalent lipid attachments and induce a strong humoral immune response. The protective effects of the immune response were not investigated. The gene encoding the P65 protein has been cloned, and its sequences and uses in vaccines and diagnostics are described in U.S. Pat. No. 5,788,962.
International Patent Publication WO 91/15593 describes five proteins of M. hyo of apparent molecular weights of 105, 90, 85, 70 and 43 kilodaltons. A full length sequence of the gene encoding 85 kilodalton protein (protein C) was provided, as were partial nucleotide sequences encoding the other four proteins.
U.S. Pat. No. 5,252,328 to Faulds discloses amino terminal sequences of immunoreactive M. hyo proteins, the molecular weights of which are 36, 41, 44, 48, 64, 68, 74.5, 79, 88.5, 96 and 121 kilodaltons. Other proteins identified based on the electrophoretic mobilities but for which no protein sequences were disclosed had apparent molecular weights of 22.5, 34 and 52 kilodaltons. While U.S. Pat. No. 5,252,328 proposed the use of these proteins in vaccine formulations, no results of vaccine trials were reported.
International Patent Publication WO 95/09870 discloses biochemical methods for the purification of M. hyo adhesions, the mycoplasmal integral membrane proteins responsible for adhesion to the cilia of the host's upper respiratory epithelium. WO 95/09870 also proposes assays and uses for these proteins, for example in vaccines and diagnostics.
A research paper by King et al. (1997; Vaccine 15:25-35) disclosed Mhp1, a 124 kilodalton adhesin that is a strain variant of P97.
A 94 kilodalton variant of P97 was identified by Wilton et al. (1998, Microbiology 144:1931-1943). Additionally, the p97 gene was shown to be part of an operon that also encodes a second protein, termed P102, of a predicted molecular weight of approximately 102 kilodaltons (Hsu et al., 1998, Gene 214:13-23). Minion and Hsu suggest the use of P102 in vaccines in the international patent publication WO 99/26664 but do not report vaccine trials.
None of the known M. hyo vaccines have been described as effective in a single dose treatment of swine at approximately 3 to 10 days of age. Such a vaccine would eliminate the need for multiple dosing and thereby significantly decrease the costs and labor associated with the worldwide massive vaccination of swine herds. Thus, there is a need for an effective M. hyo vaccine that can be administered to swine in a single dose vaccination at from about 3 to about 10 days of age for protecting and preventing diseases or disorders caused by M. hyo. 